Biogen announced this week that it will stop developing and selling aducanumab, marketed as Aduhelm, the Alzheimer's drug whose 2021 US approval divided the research and clinical community. The company says it will redirect the resources tied up in aducanumab toward lecanemab and toward developing new treatments.
Aducanumab was designed to clear amyloid, one of the hallmark proteins that accumulates in the brains of people with Alzheimer's, at an early stage of the disease. That is broadly the same approach taken by lecanemab, which Biogen co-developed, and by Eli Lilly's donanemab. The difference lies in the evidence behind them. Although aducanumab reached patients in the US in June 2021, the European Medicines Agency declined to license it, ruling that the clinical trial results were conflicting and did not demonstrate overall benefit for people with early Alzheimer's. The regulator also flagged that the studies had not shown the drug to be sufficiently safe. It was never approved in Europe or the UK.
For people with Alzheimer's in the UK, the practical impact is minimal, since the drug was never available here. The more meaningful development is what Biogen is prioritising instead. Lecanemab received full approval in the United States last year, and a UK regulatory decision is expected in the first half of 2024.
Withdrawing aducanumab does not undercut the amyloid-clearing approach itself, but it does draw a clear line between a drug whose trial data regulators found unconvincing and successors that have cleared a higher evidentiary bar. The next test of that distinction will come with the UK's decision on lecanemab.